This movie marks the first time the toys ever step outside. Chief meets a human during the course of the movie, which he also did in "Pilot". However, in Season 6, Arbiter states that they can never go outside or be seen by humans in case of them freaking out or the toys being taken away for experimenting. This has never been touched upon in the show, although fans can assume it's due to Jon Graham taking his work more seriously during the latter half of Season 4, which he said in a blog and trying to make the show more realistic (to an extent).
The latest this movie could have taken place would have been after "Cortana" yet before "Conflict Part 1", although it makes sense for the movie to take place after "Newcomers" as Chief hasn't developed a hatred for Todd and Cortana yet, which would continue into "Conflict Part 1".